What this tool means is that those with the 4.6BL iPhones (1.1.2 or 1.1.3 OTB) should now be able to downgrade their bootloader to 3.9. With the 3.9 BL installed you then could update to 1.1.3 and 04.03.13_G.
This would provide full access to all 1.1.3 features including Google Maps.
This process is extremely dangerous with any tiny mistake being capable of bricking your iPhone for good. We will be posting a tutorial soon and strongly suggest if you are determined to try this to wait for our results.